The present invention relates to a displacement sensor system for solenoid coils comprising at least two coil windings arranged one behind the other in series on a main coil body.
Displacement sensor systems for solenoid coils basically operate according to the transformer principle. Thus, an assembly of at least one primary winding, one secondary winding and one core rod is required. The core rod is generally connected with the plunger-like solenoid part of a solenoid coil and within the displacement sensor extending through the displacement distance to be measured. A pulsating auxiliary voltage is supplied to the primary winding of this arrangement. The secondary winding delivers an output signal in the form of voltage, which is modified corresponding to the displacement of the core rod. Using this basic concept, a positive signal indicating the passing of the output signal through a defined zero or neutral point can be provided when the core rod is displaced in one direction. To provide a negative signal indicating the other displacement direction, two secondary windings are required for realization of such arrangements.
DE 39 25 994 A discloses a displacement sensor system for solenoid coils according to the transformer principle. The displacement sensor system includes two coil windings wound on a main coil body and arranged one behind the other. The two coil windings are separated from one another by means of a central bridge member arranged approximately in the middle in longitudinal alignment on the main coil body. These windings make up a secondary winding. Over this pair of secondary windings and following insertion of a thin sheet between them, a pair of primary windings is laid. This pair of primary windings together form the primary winding in addition to or adjacent to the secondary winding. Using that arrangement, the mechanical toggle joinings of the start up windings and terminal end windings are as complicated as the mechanical swinging of the windings onto the relevant coil bodies, which leads to high production costs.
A transformer is described in U.S. Pat. No. 4,473,811 which uses an almost identical construction to the displacement sensor system of DE 39 25 994 A. This U.S. patent discloses a transformer with a main coil body on which a primary winding and a secondary winding are wound one over the other in each of its two sectors. Thus, the individual coils of the primary and secondary winding are connected in series.
Clark et al publication, xe2x80x9cCoaxial Transformer Bobbinxe2x80x9d, IBM Technical Disclosure Bulletin, Vol. 26, No. 6, Nov. 1983, pages 2796-2797, XP002071893, discloses an arrangement of primary and secondary coils in which the secondary winding is arranged on an additional coil body surrounding the main coil body and contacting with the primary winding. The second exterior coil body is attachable from the side. The wires of primary and secondary coils do not intersect, so that the two coil bodies actually engage on one another, but are nonetheless slidable relative to one another. These two documents, however, provide no suggestion for the execution of or even for the simplification of the mechanical toggle joining of the starting point windings and the terminal end windings.
Objects of the present invention are to provide displacement sensor systems that can be manufactured at a lower cost, with a shortened structural length and in a simplified manner.
The foregoing objects are basically obtained by a displacement sensor system for a solenoid coil comprising a main coil body, first and second primary coil windings arranged one behind another on the main coil body forming a primary winding, and first and second secondary coil windings mounted over these first and second primary coil windings forming a secondary winding. A central bridge is in a longitudinal middle of the main coil body. The central bridge has diametrically opposing pairs of toggle pin points for starting points and terminal ends of the primary and secondary windings.
Since, on the middle bridge member, toggle joining points for the starting points and the terminal ends of coil windings of primary and secondary windings are present in pairs and arranged diametrically opposite one another, the toggle joints of the starting point windings and terminal end windings to be produced are mechanical. This consequently simplifies the mechanical swinging of the windings onto the relevant coil bodies.
As a result of the central arrangement of the contact points, the structural space required for the displacement sensor system is minimized. Preferably, the toggle joining points are formed of bearing journals which can be enveloped by winding wires. Since the relevant coil windings are arranged not one behind the other, but rather one over the other, the structural length of the displacement sensor system is shortened remarkably. Since the primary windings can be wound separately from the secondary windings, a complete winding for each coil body is possible, so that costly interruptions in the winding process are avoided.
With one preferred embodiment of the displacement sensor system, the primary winding is wound on the main coil body and the two secondary windings are wound on a separate coil body, which surrounds the main coil body and contacts with the primary windings. By this means, a displacement sensor system for a solenoid coil of small structure is obtained also in radial direction.
With another preferred embodiment of the displacement sensor system of the present invention, the second or additional coil body is formed of two body halves, which can be attached to the two ends of the main coil body with its two primary coil windings. Symmetrical construction is thus attained. The coil bodies comprise essentially three individual components, which simplifies the construction. Following assembly and mounting of the primary windings, the two body halves permit winding two secondary coil windings continuously on the second coil body, which lowers overall manufacturing costs.
With another preferred embodiment of the displacement sensor system of the present invention, the central bridge includes an open perforation in the form of a wire guide. Both sides of the central bridge have contact surfaces for the attachable body halves of the second coil body. Through the groove within the central bridge arrangement, the winding or wrapping wire in turn can be guided from one side to the other side of the coil without great outlay. A position orientation of the relevant coil body relative to the central bridge is also attained through the contact surfaces.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.